Governing low-pressure turbines.



J. G. CALLAN. GOVERNING LOW PRESSURE TURBINES.

APPLIUATION FILED 1030.4, 1912.

1,09%,972. Patented Apr. 14, 1914.

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GDVBRNING'LOW PRESSURE TURBI'YNES.

APPLICATION FILED 1130.4, 1912.

Patented Apr. 14, 1914 2 SHEETS-SHEET 2.

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JOHN G. CALLAN, 013' BOSTON, MASSACHUSETTS, ASSIGNOR TO COMPANY, ACORPORATION OF NEW YORK.

GENERAL ELECTRIC GOVERNING LOW-PRESSURE TURBINES.

' Specification of Letters Patent.

Patented Apr. it, 1914.

Application filed Deeembe? 4, 1912. Serial No. 734,860.

To all whom it may concern:

Be it known that I, JOHN G. CALLAN, a citizen of the United States,residing at Boston, county of Sufi'olk, State of chusetts, have inventedcertain new and useful Improvements in Governing Low-Pressure Turbines,of which the following is a Specification.

This invention relates to elastic fluid turbines which are driven bylow-pressure steam exhausted from high-pressure engines or fromindustrial apparatus. In the case where the turbine is carrying its ownload, independent of the load on the high-pressure engine, it mayfrequently happen that the latter will drop, causing a decrease in theamount of exhaust steam furnished by said engine, and also a decrease inpressure in the receiver between engine and turbine, while the loadrequirements on the turbine may continue unchanged at full load. In thisevent, the turbine will drop a part of its load in spite of the effortsof its speed governor to prevent this by opening up the throttle valvein the low pressure main. This val ve may open its widest and yetbecause of the failure of the supply the receiver pressure will not besufiicient to en- 'able the turbine to carry its load.

My invention aims to overcome this difliculty by controlling thereceiver pressure and by re-acting through said receiver on the valvesof the high-pressure engine so that they will not be closed upon a dropin the load of said engine, but will continue to furnish suiiicicntsteam to run the turbine. I accomplish this by closing successive nozzlevalves on the turbine when the steam supply lesscns and thereby keepingup or increasing the receiver pressure by lessening the aggregate nozzlearea admitting steam to the turbine. As this receiver pressureincreases, the engine, or engines, which exhaust into it will encountercorrespondingly higher back-pressure, and will slow down whereupon itsgovernor, or their governors, will in turn admit an increased supply ofsteam. This action will go on until equi-- librium is again establishedwith the new load division. Two things tend to reestablish thisequilibrium; first, the increase of steam supply from the engine, orengines, determined by the increased back-pressure, and second, theincreased energy per pound Massaof steam available for mined by the samefact. ment, the total steam always be used by the turbine and each willhave the use of this steam through such pressure drop as is required tocarry the exact load existing at any moment. The turbine governor willindirectly influence the engine governor to furnish such amount of steamas will do the combined work of the two units, and over a widerange-between a predetermined maximum and a predetermined minimumturbine load no steam and no part of the available energy of the steamwill be wasted. The method applies essentially to the types of turbinesin which the number of nozzles in operation, or in general the steamarea at entrance, can be varied by the action of the governor. Thismethod may be combined with other governing methods in such manner asthe circumstances indicate. In fact, I prefer to provide a by-passaround the turbine to the the turbine, deter- With this arrange from theengine will condenser, which will be opened when the pose of reducingthe energy per pound of steam which is available to the turbine,

there will be momentary reverse effect, due

to the discharge of stored steam from the receiver, and the partialevaporation of any water which may have accumulated there. This wouldcause the turbine to show a momentary rise in speed and load, althoughthe governor would be acting to reduce bothv these. Obviously this wouldcause a further opening of valves and consequently an unstablecondition. For this reason, I prefor to arrange the bypass around theturbine so that it is opened by any sudden opening movements of thevalve gear and to add a vacuum-breaking device, which ispreferably-actuated whenever the governor acts so quickly to increasethe area of steam entrance that even the opening of the by-pass is notsutticient. This vacuum breaker may -85 a 7 and8andclosein reverseorder. Asimple to e equalizing "also be actuated to preventrrunaway atzero load if required. addition 'to' all this,

1 may arrange. means for admitting liv" steam at high pressurefintothereceiver on the. quickclosing' of the turbine valves, thus promptlyraising this pressure when necessary, andmaintaining the s eed on suddengload increase as on Isudden cad-reduction;

supply any temporary shortage due mixed-pressure machine, I prefertoarrange treme-low load on the engines.

In the accompanying'drawmgs,

Figural ispan end elevation of a lotvressure turbine of the Curtistype,embti ying my infvention; Fig; 2 is aside elevation on a larger scale ofthe governing end -of sald turblne, A partly in seet1on,-and Fig. 3 is'asectlonion' 'erates the by-pass.

a 'still'larger' scale ofjthe dash-pot whichop- The, turbine shown-1s ahorizontal its:

' ch'ine-receivin 'lowrp ressure steam through a main 1 an through, thepipe 2.. The main conveysthe steam to a chamber 3-.fro1nwhich itisadmitted by valves 4; to nozzles 45,, 6, 7 and 8.-

A, fifth nozzle 9, is permanently open. The nozzles 5 and 6 are actuatedsuccessively by so. a controlled by a pilot-valve 11.. A similara motor,preferably "a hydraulic cylinder 10 I motor 12,- also controlled by saidpilot valve,

actuates the nozzles -7-and 18; the arrangement of the pilot valve andmechanism being such that the nozzles open inthe'ordent), 6,

- form ofv-alve-operating mechanism is illus-v tratedQcoinprising a bar13 attached to"th e "engaging with its slots. "The-'lowerslot in.

piston rod of the motor and containingcam slots 14,- 15, one for eachvalve. Qn each valve,stemfll 6 is a head 17 having a 'pii118 each baropensits valve before the upper s lotyacts and .has an extension.permitting}- sufficient movement I of the bar to opensaid; i uppervalvewithout disturbing the already;

, open lower valve.

The pilot valve ste'ni .1!)-is pivoted to a fioating lever 20-linked'to' the. arm 21 of the piston rod 24 ofa ove'rnor 22 and pivotedto an air-23 which is pivoted to the two bars '13. Attached to this'ecjua'lizer. i s valved piston 25,

the speed,

forming one element. -of a dash-potlwhose passBO extending around theturbine-from. the main 1 to the pipe 2. A finger 31' on the."

cylinderorshell 26is supportedi on a rod 27.

-A rock-arm 28 is pivoted to said; rod and serves to actuate" athrottleva'lve 29 in a by-v spindle of the throttle valve, which is preferably0f the butterfi typefl is.- adapted.

-. to come in contact Withthe stem 32 of a 'vamiu-m-breaking valve inthe by-pass on the con'denser sideof the throttle valve.

as Leading into the main 1, preferably -at anis connected by exhaustingto fa condenser v d any greater. back-pressure inthe receiverv elbow oftheby-pasal is apipe connected 2 rod 27 through suitablemechanism, suchas a lever 35- linked tenants: lever 36 whicha spring 31 with therockamas The ope'ration as follows: With mini-' mum load on thexturbine,the-nozzle 9, which is always open, issupplem ented by thenoz-f' zles 5,,6, I7, 8, which under these conditions are also open, both cam bars 13being raised 1 totheirhighcst point. The amountof steam fedto theturbine is determined by some other source, which maybe variable independently' of vthe load on the turbine such for example, as two or threeengines vvorkliver, and let out of itjust as muc energy 1 as the furine' loa'd requires, while .at the ingon independent loads and allexhaust-j 'ing into a common receiver from which the main 1 leadstojthe' turbine.- The problem is: to take all the steam which the enines desame time never imposing upon the engines with all'th'e' nozzlevalves open, the amount of steam delivered to the turbine willpassthrough it and to the condenser with arela'- tively smalldrop'ofpressure. On the other hand, as the load on the turbine increasedtheresulting drop-in speed causes the speed I governor 22 to lift the pilotvalve 11 and 7 start the motor 12, ivliichpull's down its bar 13 andcloses the valve 8, thus increasing the 'pressurevdrop through theturbine and con-. .sequently the energy derived by the turbine from agiven amount of steam passing. {As

a con'seqr1ence, the pressure ii the, receiver fro1n wh1oh the turbinederives tssupply will be\increased,thus compelling the en;

eratefund er less favorable conditions and causing them to deliver alarger volume of steam. This adds to the. other eiiechsince the turbinenow not only derives more en ergy from each pound'of steam which passesthrough it, but it s also receives more steam.

Asfujrther load vis placed .upon t'he turhine,

the governor will close successively the valves of nozzles-7, (i'and 5.The receiver pressure will of, course be progressively in--creasedbythis action, and "when all the valves are closed and steamisfadmitted only at' the nozzle-9, which is always open, the turbine isdelivering the maximum load it can without resort to additional high:presg sure steamh Under these conditions the pounds above atmospherepressure.v

" If'the't urbine is not. a-mixed pressure Inagines which exhaust intothe-receiverto opf pressure in, the receiver may be several 12s jc'hine,thatdis, has no valves to admit high 1 downward movement of the cam bars13 the the rod 27 will be forced down against the tension of the spring37 whose upper end is held stationary by the arm 28. The rod has acollar 38 engaging with the lever 36 which thereby actuated and opensthe .valve 34. This admits boiler steam to the recei'v 7 and furnishesthe turbine with additional energy to meet the additional load. If it isdesired to admit'live steam to the receiver when the turbine valves areclosed with unusual.suddenness as explained in a preceding paragraphthen the valve 39, Fig.

will not occur. mine whether such a response is desirable 3, is omittedand the by-pass 40 constitutes the only communication between the upperand lower end of the dash pot. Under these conditions a sudden downwardmotion of the equalizer 23 will act through the liquid in the dash-pot,which cannot instantly escape, to momentarily open the valve 34; butthis valve will continually tend to close again under the influence ofthe spring 37 and the relatively slow flow of liquid through 40 willallow such closure soon after rapid downward motion of 23 ceases. If thevalve 39 is provided as shown, then this temporary admission of livesteam in response to sudden downward movement of equalizer 23Circumstances will deteror not. If the load on the low pressure turbinefluctuates violently and the receiver or pi )ing furnishing its steam isof considerab e capacity, then valve 39 should be permanently closed,since under these conditions the action just explained will be highlydesirable in maintaining regulation.

Where reverse conditions obtain, valve 39 should be operative in orderto minimize the amount of liveeund therefore expensive steam sent diectly into the receiver. I prefer'to so design valve 39 that it may bethrown out of operation or left in operation as the demands of theservice require. This maybe accomphshed by providing a set screw adaptedto clamp the valve to its seat or to be backed ofi so that the valve isoperative. Now-on the other hand, assume a reduction in. the load on theturbine. The governor at once causes the motors 10 and 12 to open thevalves 5, 6, 7, 8 in succession.

The lifting of the bar 23 lifts the plunger '25, and the mass of liquidabove said plunger communicates its movement to the shell which riseswith it, lifting the rod 27, Sadting off the live steam valve 3-4, andopening the by-pass throttle 29. The dash pot has a controllable andadjustable by-pass 40 so that if the upward movement of the bar 23 isslow and gentle, the rod 27 may not be plying steam thereto,

erate steadily at all times. Now assume that 1 the load on theturbinebecomes so light that the opening of all the nozzle valves does not meetthe conditions. will by this time have been lifted so far that theplunger 28 will strike the top of the dash pot. Any further lifting ofthe bar by the action of the governor will cause a positive lift on therod 27 and an opening of the throttle valve 29in the by-pass 30. This,and the possible breaking of the vacuum also, will meet the situationsupposed.

In accordance with the provisions of the patent statutes, I havedescribed the principle of operation of my invention,.together with theapparatus which I now consider to represent the best embodiment thereof;but I desire to have it understood that the apparatus shown is onlyillustrative, and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. The combination with a low pressure turbine connected to receve theexhaust from a high pressure engine, of a source of steam supplyconnected to said low pressure turbine, a valve controlling said source,valve means for varying the area of admis sion to said low pressureturbine, a speed governor, and means controlled by said governor tofirst operate said valve means to de crease the effective area ofadmission upon adecrease of speed, and to then operate said valve toadmit steam from said source to said low pressure turbine.

- 2. The combination with a low pressure turbine connected to receivethe exhaust from a high pressure engine, of valve means for varying thearea. of admission to said low pressure turbine, a normally closedbypass around said turbine, a speed governor, and means controlled bysaid governor to first operate said valve means to increase theeffective jarea of admission upon an increase of speed and to then opensaid by pass.

3. The combination with a low-pressure turbine, of a connection forsupplying steam thereto from the exhaust of a high pressure engine,valve means for varying the area of admission to said low pressureturbine, a

The equalizer bar 23 conduit joined to said connection for supa normallyclosed valve in said conduit, a speed governor, and means controlled bysaid governor to first operate said va ve means to decrease theeffective" area of admission uponlan. increase in load andto then opensaid-valve toadmit steam to said connection.

. 4. 'The combination with ailow pressure turbine of a connection forsupplying steam thereto from the exhaust of ahigh pressure engine, valvemeans forjvary-ing the area ofadmission to said low pressure turbine, anormally closed lby-pass around saidtur-bine',

'10 a'speed governor, means controlled by said governor to operate saidvalve means to increase the effective area of admission upon an increaseof speed, and further means 0011-" trolledby said governor totemporarily opensaid by-pa'ss upon a rapi'd operation of said valvemeans'to increasethe effective area of admission. f '5. The comb1nat1onWith. a low pressure jturbine supplied with steam from a receiverconnected with. independently loaded en- -gines, of a plurality ofnozzle valves, a'speed governor, and mechanism enabling'said gov- -ernorto' close said .valves 'in. succession, as

the speed drops, and vice versa.

6-; The combination with a low pressure turbine supplied with steam froma receiver connected With'independe'ntly loaded en' gines, of a'plurality ofnozzle valves, a speed v "governor,-means Whereby saidgovernor will close saidrvalves in succession as'the speed drops, andmeansenabling said governor to admit live steam to the receiver-when allsaid; nozzle .valves have been closed.

"T. The combination with a low pressure turbine supplied with steam froma receiver '40 on the turbine drops.

. over-nor andjmeans Whereb .said overn'or connected withindependently-loaded engine's, of a plurality of nozzle valves, a speed,goveaiior', and means whereby said governor.

will succe'ssivelyopen said valves as the load 8. The-combination With alow pressure turbine supplied with steam from a receiver connected with;independently loaded engines, of a plurality of nozzle valves,a speedwillsuecess'ively open said valves as the load on the-turbine drops,a-by-pass around said turbine, and means whereby said' can-open said bypass when said nozzle valves have allbeen opened.

bars for operating them, motors for actuating said'bars, a speedgovernor controlling said motors, a by-pass around said turbine, athrottle valve in said by-pass, and a dash I pot having oneelementmoving with. said bars, and the other connected to said throttlevalve. j l

10. vThe combination with a low pressure turbine supplied with steamfrom a receiver, of a plurality 'ofnozzle valves, cam bars for 9. Thecombination with a low pressure turbine, of a plurality ofnozzle valves,cam

overnor 3 operating said valves, motors for actuating "said bars, aspeed governor controlling said motors, a valve admlttmg hve steamlDOSEtld receiver, and a dash pot having one elementmoving' with saidbars and the other opera tively connected with said live steam valve. 11The .combination'vvith a lowpressure turbine supplied with steam from areceiver,

of tWo-pairs'of nozzlevalves, a cam bar for successively operating thevalves in each pair, a motor .for'- each bar, a pilot valve commontoboth motors, a speed governor controlling said pilot valve, an; eualizer connecting the two cam bars, ay-pass around said turb1ne,athrottle valve. in said by-pass, a valveddash pot plunger attached tosaid equalizer, a shell cooperating with said-plunger, and arodsecur'ed'to said shell and adapted to operate said throttle valve.

12. The combination with a low pressure turbine, supplied with steamfrom a-receiver, .of a permanently open nozzle, a plurality of nozzlesprovided with valves, and a speed. governor operating to close saidvalves upon- CAEL F. VVooDs.

